The present invention relates to a method of making a laser diode and particularly to such a method which provides for good electrical contact to the diode.
Recently there have been developed several different structures of semiconductor lasers which are capable of continuous operation at room temperature. One structure, as shown in U.S. Pat. No. 3,740,661 of L. A. D'Asaro, entitled "MINOR LOBE SUPPRESSION IN SEMICONDUCTOR INJECTION LASERS", issued June 19, 1973, uses a stripe contact on one surface of the semiconductor body to achieve confinement of the path of the electrical current across the active region of the laser. However, this structure has the disadvantage that the current spreads out as it passes across the body of the laser so that the width of the active region is difficult to control.
To overcome this problem a structure has been developed in which current confinement is achieved by a narrow diffused region extending from the surface of the body to a point adjacent the active region of the laser. Such a structure is shown in U.S. Pat. No. 29,866 to H. Yonezu, entitled "DOUBLE HETEROSTRUCTURE STRIPE GEOMETRY SEMICONDUCTOR LASER DEVICE" issued Dec. 19, 1978. A problem with this structure is in achieving good electrical contact to the surface of the semiconductor body having the diffused stripe therein. Because of the type of materials generally used for the laser, it is difficult to achieve a high concentration of conductivity modifiers at the surface of the stripe to provide a low resistance contact to the stripe. The laser is generally made by epitaxially growing the various layers on a substrate; because of the materials used it is difficult to achieve good adhesion of the metal contact layer to the finally grown layer.